Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Amortized Cost
Available for Sale, Due in one year or less	$ 3,500
Available for Sale, Due after one year through five years	2,204
Available for Sale, Due after five years through ten years	0
Available for Sale, Due after ten years	0
Available for Sale, Total debt securities	5,704
Investment securities available for sale, amortized cost	4,342,007	$ 4,724,895
Fair Value
Available for Sale, Due in one year or less	3,489
Available for Sale, Due after one year through five years	2,205
Available for Sale, Due after five years through ten years	0
Available for Sale, Due after ten years	0
Available for Sale, Total debt securities	5,694
Investment securities available for sale, at fair value	$ 4,300,490	4,680,226
Ratio of Fair Value to Amortized Cost	99.00%
Amortized Cost
Held to Maturity, Due in one year or less	$ 41,148
Held to Maturity, Due after one year through five years	252,007
Held to Maturity, Due after five years through ten years	248,861
Held to Maturity, Due after ten years	589,510
Held to Maturity, Debt Securities, Amortized Cost Basis	1,131,526
Held to Maturity Amortized Cost	1,554,843	1,273,536
Fair Value
Held to Maturity, Due in one year or less	32,101
Held to Maturity, Due after one year through five years	259,468
Held to Maturity, Due after five years through ten years	250,081
Held to Maturity, Due after ten years	587,547
Held to Maturity, Securities, Debt Securities	1,129,197
Held to Maturity, Total debt securities	$ 1,550,322	1,264,674
Ratio of Fair Value to Amortized Cost	99.70%
Private Label
Amortized Cost
Investment securities available for sale, amortized cost	$ 1,118	1,134
Fair Value
Investment securities available for sale, at fair value	1,102	1,121
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
GNMA Commercial Mortgage-Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	1,696,287	2,064,508
Fair Value
Investment securities available for sale, at fair value	1,663,337	2,028,898
Amortized Cost
Held to Maturity Amortized Cost	296,232
Fair Value
Held to Maturity, Total debt securities	294,980
Equity Securities [Member]
Amortized Cost
Investment securities available for sale, amortized cost	18
Fair Value
Investment securities available for sale, at fair value	112
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
FNMA and FHLMC \| Residential Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	575,826	625,234
Fair Value
Investment securities available for sale, at fair value	590,419	639,930
Amortized Cost
Held to Maturity Amortized Cost	38,829	37,697
Fair Value
Held to Maturity, Total debt securities	38,505	37,443
GNMA \| Residential Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	2,063,054	2,028,301
Fair Value
Investment securities available for sale, at fair value	2,039,826	2,004,475
Amortized Cost
Held to Maturity Amortized Cost	88,256	89,996
Fair Value
Held to Maturity, Total debt securities	$ 87,640	$ 89,556

Held-to-maturity Debt Securities, Amortized Cost Basis

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